Operative Dentistry I: Amalgam Restoration II

Operative Dentistry I: Amalgam Restoration and Manipulation II

• Course offered by Dr. Luluah K. Alhagas, Assistant Professor in Operative Dentistry, Batterjee Medical College, 2024.

Lecture Objectives

• Identify amalgam cavity preparations.
• Identify amalgam manipulations.
• Recognize amalgam safety precautions.

Dental Amalgam Cavity Preparation

• A pre-operative assessment of the case is necessary, including medical/dental history, radiographs (OPG, BW), chief complaint, and dental screening.

Local Anesthesia

• Local anesthesia procedures are a part of the preparation process

Isolation

• Isolation techniques are crucial for the procedure.

Cavity Preparation: General Requirements

• Remove defects like caries and faulty restorations.
• Extend the preparation onto sound enamel.
• Establish a 90-degree cavosurface margin.
• Maintain a minimum thickness of 1.5-2 mm.
• Prepare undercuts appropriately.
• Add supplemental features like grooves, slots, pins, and/or cove as needed.

Cavity Preparation: Cavity Principles

• Establish initial tooth preparation depth.
• Outline form.
• Cavosurface margin.
• Primary retention form.
• Primary resistance form.
• Convenience form.

Initial Tooth Preparation Depth

• Pulpal floor depth: 1.5 mm from central groove.
• DEJ depth: 3 mm from central groove.
• Axial wall depth: measures from DEJ to axial wall.

Outline Form/Cavosurface Margin

• The cavosurface margin should be at a 90-degree angle.

Retention Form

• Primary retention prevents dislodgement during insertion.
• Secondary retention adds support with locks, coves, pins, and slots

Resistance Form

• Primary resistance prevents dislodgement from apical or oblique forces.
• Cusp and marginal ridges are preserved.
• Walls are prepared perpendicular to occlusal forces.
• Rounded internal preparation angles are maintained.
• Unsupported or weakened tooth structures are removed.

Convenience Form

• Features that improve accessibility for caries removal, matrix placement, and amalgam insertion.
• Proximal margins are extended to create space from adjacent teeth.

Dental Amalgam Manipulation

• Alloy selection, Proportion of alloy, Trituration of alloy, Condensation of amalgam mix, Finishing/polishing of the Restoration, Carving of the Restoration, Burnishing of the Restoration, Checking occlusion, Checking margin, and Amalgam Carrier, Amalgam Safety Precautions are all part of the manipulation process.

Alloy Selection

• Alloy choice depends on the specific case, considering particle shape, copper content, and zinc content.

Alloy Proportion

• The ratio of alloy to mercury is typically 1:1.
• An adequate amount of mercury coats alloy particles to create a homogeneous amalgam mix.
• Insufficient mercury causes uncoated particles, resulting in a dry/friable amalgam mix.
• Excessive mercury results in a weak amalgam and excess creep/flow.

Trituration Proportion

• Trituration involves mixing mercury and alloy particles until a homogeneous, plastic mass of condensable amalgam is formed.

Under-Trituration & Over-Trituration

• Insufficient mixing of mercury and alloy results in under-trituration, presenting a dull and fragile mixture.
• Excessive mixing results in over-trituration, leading to a shiny and hard mixture.

Amalgam Carrier

• Amalgam carriers are specialized tools for handling and placing amalgam.

Condensation of Amalgam Mix

• Increase adaptation by incorporating excess mercury to the surface.
• Increase amalgam density.
• Increase final strength by overfilling cavity by 1mm

Burnishing of Amalgam Restoration

• To remove excess mercury from the surface.
• to provide guidelines for amalgam carving.
• to increase adaptation at the restoration margin

Carving of Amalgam Restoration

• Restore normal tooth anatomy and contour.
• Improve adaptation at the restoration margin.

Checking Occlusion

• Occlusion is checked to ensure proper contact and function.

Checking Margin

• Methods for evaluating the integrity of the amalgam's margin.
• Flash margin: Explorer tip catches the tooth to amalgam.
• Submargin/ditch: Explorer tip catches the amalgam to tooth.
• Open margin: Explorer tip catches in both directions.

Finishing/Polishing of Amalgam Restoration

• Reduce plaque retention.
• Reduce tarnish and corrosion.

Dental Amalgam Safety Precautions

• Proper disposal of amalgam debris (scrap on bracket table, amalgamator aerosol, amalgam scrap container, amalgam waste , mercury in plumbing traps).